


Promises

by Firehedgehog, Snowstorm174



Category: Kingdom Hearts, Undertale (Video Game)
Genre: Alternate Universe - Errortale (Undertale), Alternate Universe - Underswap (Undertale), Gen, M/M, Post-Kingdom Hearts III, Reincarnation, Riku Is Not Okay With Sora Disappearing (Kingdom Hearts), Riku Is So Done (Kingdom Hearts), Underswap Sans (Undertale)
Language: English
Status: In-Progress
Published: 2019-12-29
Updated: 2020-01-01
Packaged: 2021-02-27 06:13:38
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 1,253
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22022371
Author URL: https://archiveofourown.org/users/Firehedgehog/pseuds/Firehedgehog, https://archiveofourown.org/users/Snowstorm174/pseuds/Snowstorm174
Summary: Sora made a promise, and kept it, completing his destiny. Reincarnation was just another adventure for him.Blue is very confused, and Error thinks it's all rather entertaining to watch.Riku, on the other hand..."Sora, get back here! Our story isn't over yet... I'm not ready to let you go!"
Relationships: Blue & Error (Undertale), Riku/Sora (Kingdom Hearts)
Kudos: 53





	1. Chapter One: A Promise Kept

_He had no regrets._

_That, Sora knew._

_He’d had his adventures._

_He’d seen the unseen, he’d known both light and darkness._

_He’d saved the lost, died and then lived again._

_Lost his heart, and gotten it back._

_He knew what good and evil were._

_Kairi was safe and alive, and he knew that Riku would keep her safe._

_Sora stepped into the next great adventure._

_And awoke to a new fate..._

For as long as he’d been alive, Sans had known there was something different about himself.

It wasn’t the discovery of the resets.

Or the other AU’s.

Or the fact he had too much magic for his body.

There was just... something different.

He didn’t quite understand it.

Hopefully he’d figure it out.

He did have annoyances, though. He was the original Swap Sans, nearly as old as Classic, and it annoyed him greatly that he was ridiculously short. At just over four feet tall, he was tiny, the size of a child, and people kept on acting like he was a freaking kid.

He was the same age as Pappy, they were twins.

He had heard that a copy of his joined the Star Sanses.

Why anyone want to join them he wasn’t sure. Dream seemed to walk past the obvious clues that Nightmare would really like Dream to leave him alone, and Ink seemed... empty in a way that seemed _wrong._

_‘Worse state then a nobody, he can’t even gain a heart…’_

He ignored the sad voice in his head that popped up now and then.

And the other swap, his copy, was, to his great annoyance, much taller then him.

He judged things much too quickly for Sans’ liking.

The Star Sanses were a disaster in the making.

Then, Error came, appearing seeming out of nowhere. There had been a lot of AUs becoming corrupted and collapsing, and not much later, his brother had warned him about a monster destroying AUs, one whom he’d apparently heard of from Ink.

Error had come their AU, and begun to try and destroy it- and then, Sans had the first class seat on kidnapping 101.

He’d gained a nickname of his own.

Blue… he liked it, he was no longer just ‘Swap’ to visitors.

Error was broken, shattered his soul cracked and held together with strings, but… he was still strangely familiar.

Lost in insanity from loneliness, dragged away from his world.

‘His heart is almost lost,’ the voice whispered. ‘And so familiar…’

‘Why can’t I remember?’ Blue and the voice thought at the same time.

Blue couldn’t leave the destroyer like this, so lost and alone in a world of endless white.

Befriending such a broken person wasn’t easy.

Especially when the Anti-Void began to effect him.

“You’re my friend, no matter what happens,” Blue told Error.

Then, Error released him with Chara’s soul, letting him reset his AU.

“We’ll see each other again, Error. After all, my friends are my power!” Blue said, smiling happily.

That was a promise he would be sure to keep.

OoOoO

A strange expression, almost a smile, crossed Error’s face.

‘He always did keep his promises,’ whispered one of the voices faintly- wait, was it one of the voices? He’d never heard that one before…

The whisper in Error’s heart smiled contentedly, the effort of reaching past the glitches to speak having used up what little energy he had managed to regain after his leap across worldlines.


	2. Chapter Two: What was Lost

**Summary for the Chapter:**

> Darn it Sora, just why?

**Notes for the Chapter:**

> Here is chapter two from Snow and I, have no clue when the next chapter will be due to work and Snow being distracted by Pokemon.

“No... no!” Riku cried in frustration.

After all this, everything they’d been through…

Sora was gone.

He’d been standing there.

And then... he’d vanished.

“You stupid idiot!” he screamed to the sky.

It had been two days since that day on the beach, a moment of happiness followed by horror.

He looked up at the night sky, the stars shining without a care.

He’d admit to pounding the sandy beach in a tantrum.

He gave the sand one last punch.

Placing a hand over his heart, Riku paused.

It was faint, frail, thin as a single strand of a spiderweb... but it was there.

“Sora?” he asked, confused.

After all, Sora was dead… right? He shouldn’t be able to feel any bond to Sora now… especially not the one from him being Sora’s Dream Eater.

He got up and started running for the Gummiship- it was time to pay a visit to a certain sorcerer (whose name is Disney spelled backwards).

OoOoO

“Curious, very curious,” Yen Sid said as his magic flowed over the silver-haired teen’s body.

Riku shivered, he really didn’t like the feel of the other’s magic on him.

Oh, he knew the wizard was a good person.

But his magic didn’t really agree with him.

He knew it was due to the darkness in him, from his days of stupidity.

‘Full speed ahead, let’s jump into the darkness!’ he thought sarcastically, he really had been an idiot back then.

“Is there any way to use it to find Sora?” He asked hopefully.

“Yes...” Yen said “And no.”

“That’s... not very helpful, can you please give me a solid answer,” Riku growled, his irritation showing.

“Riku, please calm down,” Mickey said.

Riku took deep, calming breaths, and to his relief, Yen Sid stopped using his magic on him as well, which made him feel much better.

“Please explain,” Mickey said as Riku cooled down.

“Sora has already passed on, he cannot be found and put back togeather,” Yen Sid said, calmly sipping his tea. “Not even the power of waking can bring him back here.”

“But then why am I still linked to him?” Riku asked, bewildered.

“What do you know of reincarnation of the soul?” the elder man asked.

‘Why Sora... why are you like this?!’ Riku mentally cried.

OoOoO

In another multiverse of magic, monsters, and souls, a small skeleton monster sneezed.

He soon forgot about it as his world reset again, his soul shattering for a millisecond before being recreated.

OoOoO

“But... he’d be a baby,” Riku said unhappily. Sure, the thought of a baby Sora made him silently aww, but still... he wanted _his_ Sora, not a baby.

“Not exactly. Souls rarely reincarnate in the same multiverse, or even the same Omniverse,” Yen Sid said, pulling out a book. “Often they even ignore timelines entirely.”

Riku’s eye twitched.

“Your tie to Sora goes through to another omniverse. Time could very well go very different there, he could have grown to an adult in a blink of an eye,” the man said.

Riku felt ill. Sora literally could have died of old age, and he’d never even know.

“Tell me how to get there, now,” Riku said, his grip crushing a bit of the table.

“We could use you for the new dangers that Master Aqua sensed,” Yen Sid said dryly.

Riku gave the man a smile that was nowhere near friendly. For some reason, the elder male rubbed him the wrong way from time to time.

“Sora gave up _everything_ for us, so why would I not give up everything for him,” Riku said, his eyes like aquamarine steel.

Yen Sid looked as if he aged a hundred years in an instant.

“I can only give you this book, what you seek is beyond me,” Yen Sid said, pushing a large book towards the silver-haired keyblade master.

“Thank you,” Riku said, taking the book and getting ready to leave.

“Tell Sora... I’m sorry,” Yen Sid said.

“For some things, it’s too late for apologies,” Riku replied as he slipped out the door.


End file.
